Grout is a particularly fluid form of
concrete used to fill gaps. It is used in
construction to embed
rebars in
masonry walls, connect sections of pre-cast
concrete, fill voids, and seal joints such as those between
tiles. Grout is generally a mixture of
water,
cement,
sand, often color tint, and sometimes fine gravel (if it is being used to fill large spaces such as the cores of concrete blocks). Unlike other structural pastes such as plaster or
joint compound, correctly-mixed and -applied grout forms a waterproof seal.